获取synchronized锁中的阻塞队列中的线程是非公平的

Posted 2020-07-13 沧海一滴

 

synchronized中阻塞队列的线程是非公平的

 

测试demo:

import java.text.MessageFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.TimeUnit;

public class SleepState {

    public static ThreadLocal<SimpleDateFormat> threadLocal = new ThreadLocal<SimpleDateFormat>() {
        @Override
        protected SimpleDateFormat initialValue() {
            return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSZ");
        }
    };

    private static final int[] lock = new int[0];

    public static void main(String[] args) throws InterruptedException {
        Thread thread1 = new Thread(new TestSynchronizedTask(lock, 1000 * 10), "Thread1");
        Thread thread2 = new Thread(new TestSynchronizedTask(lock, 10), "Thread2");
        Thread thread3 = new Thread(new TestSynchronizedTask(lock, 1000), "Thread3");
        thread1.start();
        TimeUnit.MILLISECONDS.sleep(1000);
        thread2.start();
        TimeUnit.MILLISECONDS.sleep(1000);
        thread3.start();
    }
}

class TestSynchronizedTask implements Runnable {
    private final int[] lock;
    private int sleepMilliSeconds;

    public TestSynchronizedTask(int[] lock, int sleepMilliSeconds) {
        this.lock = lock;
        this.sleepMilliSeconds = sleepMilliSeconds;
    }

    public TestSynchronizedTask(int[] lock) {
        this(lock, 0);
    }

    @Override
    public void run() {
        synchronized (lock) {
            try {
                System.out.println(MessageFormat.format(" {0} {1}  begin", SleepState.threadLocal.get().format(new Date()), Thread.currentThread()));
                TimeUnit.MILLISECONDS.sleep(sleepMilliSeconds);
                System.out.println(MessageFormat.format("{0} {1}  will end", SleepState.threadLocal.get().format(new Date()), Thread.currentThread()));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

 

执行结果：
 2016-05-26 13:31:44.260+0800 Thread[Thread1,5,main]  begin
2016-05-26 13:31:54.260+0800 Thread[Thread1,5,main]  will end
 2016-05-26 13:31:54.260+0800 Thread[Thread3,5,main]  begin
2016-05-26 13:31:55.260+0800 Thread[Thread3,5,main]  will end
 2016-05-26 13:31:55.260+0800 Thread[Thread2,5,main]  begin
2016-05-26 13:31:55.276+0800 Thread[Thread2,5,main]  will end